1. Field of the Invention
The present invention relates to an image forming apparatus, and more particularly to an image forming apparatus that forms an image by causing a toner, which has been made to fly from a toner carrier, to fly and adhere to recording medium means by way of toner passage holes the opening and closing of which is controlled.
2. Description of the Related Art
An image forming apparatus of the type that directly records an image on a recording medium (comprising an intermediate transfer medium) using toner (recording material), which is called toner jet, direct toning, toner projection and the like, is known as a conventional image forming apparatus.
For example, Japanese Patent Laid-open No. 63-136058 (referred to as Prior Art 1) discloses an image forming apparatus that uses frictional electrification between either fixed plates or rotating rollers to apply an electrification charge to toner supplied from a toner hopper, and after rotational feeding, controls the flight of the toner with an electric field between a control pulse applied to a control member and the rotating rollers. Toner having an electrification charge is electrostatically adhered to the surface of the rotating roller here, and this toner must be separated using a control pulse. This is problematic in that, since there is a gap of several hundred micrometers or more between the rotating roller and the control member, the control pulse applied for separation must inevitably have a high voltage of 500V or more, and the cost of the driver needed to control the number of picture elements is extremely expensive. Another problem is poor responsiveness and time delays associated with causing the toner adhered to the rotating roller to separate and fly.
Further, Japanese Patent No. 2933930 (referred to as Prior Art 2) and Japanese Patent Publication No. 2-52260 (referred to as Prior Art 3) disclose an image forming apparatus that applies a control pulse to a control electrode through which the developer passes, while applying an alternating bias between a rotating developer support and control means. Although this constitution alleviates the problem of responsiveness associated to the apparatus disclosed in the above-mentioned Prior Art 1, a uniform alternating field is applied to the entire flying area of the toner, repeating the time that the developer is adhered to the developer support and the flying state. For this reason, a strong alternating bias must be applied for separating the developer that is adhered to the developer support, causing a major reliability problem in that there is no way to avoid the separated toner flying with great force to the control means side, and large amounts of developer adhering to the control means electrode. Furthermore, this constitution cannot solve the problem of driver cost since the same gap as mentioned hereinabove exists between the developer support and the control means, and a high voltage value of 500V or more is applied between the two, requiring that the control pulse that forms the field that either passes or blocks the developer to/from this field be a similarly high voltage value.
Conversely, Japanese Patent Laid-open No. 59-181370 (referred to as Prior Art 4) discloses a constitution, which has a plurality of electrodes in a developer carrier, and causes the toner to fly to the control electrode side by forming a temporally changing electric field between these electrodes. Since the passage of toner that is flying and floating in the proximity of the control electrode is controlled here, the problem of the high control voltage of the apparatuses of Prior Art 1 through Prior Art 3 is resolved.
Further, Japanese Patent Laid-open No. 02-226261 (referred to as Prior Art 5), similar to the above Prior Art 4, discloses a constitution, which has a plurality of electrodes in a developer carrier, and which causes the toner to fly by forming a temporally changing electric field between these electrodes, and a control electrode for controlling the passage of the toner, which had heretofore been installed on the recording medium side, is installed on the toner supply side. It is disclosed that in this constitution, the control voltage, which had to be 400V in the conventional apparatus, can be 100V, and when the toner that adheres to the print head, on which the control electrode is provided, is removed, this toner can be returned to the toner supply source.
Further, Japanese Patent National Phase Publication No. 2001-505146 (referred to as Prior Art 6) discloses a constitution, which uses a rotating cylindrical sleeve to supply toner, and which applies a static electric force that allows the toner to pass through an aperture via a uniform electrical field between the print head surface potential and the sleeve, provides a deflecting electrode that is paired on the print head surface side with the control electrodes surrounding the aperture, and raises the print dot density in the main scanning direction. It is disclosed that a guard electrode is disposed between the control electrodes that control the passage of the toner here to prevent interaction between the control fields.
Further, Japanese Patent Laid-open No. 11-301014 (referred to as Prior Art 7) discloses the disposition of a control electrode, which supplies toner via a toner supply roller, and which controls the flight of the toner on the toner supply roller side of the aperture containing member, and a deflecting electrode, which deflects the flight path of the toner.
Conversely, Japanese Patent No. 3290513 (referred to as Prior Art 8) discloses that after forming a toner image on the surface of the recording paper, a fixing agent is either sprayed or dripped onto the recording paper surface to affix the toner to the recording paper by either dissolving or swelling the toner. Further, Japanese Patent Laid-open No. 2004-109747 (referred to as Prior Art 9) discloses that the toner is affixed by applying a dissolving agent only to the toner image part of the carrier surface of a toner image formed using a water-repelling intermediate transfer unit. These Prior Arts are both systems for producing an output image by developing, transferring and fixing toner to an image carrier that forms a conventional latent image, and are fixing techniques that do not require high heating energy. However, the constitution of Prior Art 8 has a major drawback in that it is difficult to control the micro amounts of fixing agent applied to the recording paper, giving rise to wrinkling and curling of the recording paper. Further, although Prior Art 8 resolves the problem of wrinkling and curling in particular by applying a foam fixing solution to the toner of the intermediate transfer unit, there is no disclosure about controlling the amount of the foam fixing solution that is applied.
Thus, a conventional direct recording-type image forming apparatus has problems, such as the fact that the toner adheres to the surface of toner controlling means and around the toner passage holes, the ON/OFF control of the passage of the toner cannot be stably controlled, and toner utilization efficiency is inadequate.
In addition, the problem right from the start is that in an apparatus in which a direct recording method forms an image by adhering toner to the imaging surface of recording medium means, when the toner collides with the imaging surface, the toner spatters and decreases the image quality.